Tying up or worse?

Most of us can remember a time when we have played the role of weekend
warrior and paid dearly for our sudden bout of athleticism during the next few
days. Many will acknowledge that they have treated their horses in a similar way as
well. How do you know if your horse is just tired and stiff after that longer than
expected trail ride or has tied up? The following information will help you
understand the signs, degrees of severity, treatment, and management of tying up disease
or rhabdomyolosis.

Rhabdomyolosis, (breakdown of striated muscles after exercise) is
described by many different names depending on severity and, often, geographical
location. Some of these names include: tying up, azoturia, myoglobinurea, set-fast,
black water disease, and Monday morning disease. The disease often can be identified
in draft horse breeds that perform hard work during the week, and are rested on the
weekends without a decrease in their grain ration. Back on the job on Monday
morning, the horses begin to cramp up, show hindquarter stiffness, severe muscle pain and
pass very dark urine. One of the suggested mechanisms is that excess glycogen is
accumulated in the muscle while the horse is resting at full ration, and this is quickly
broken down into lactic acid when he begins work. The high lactic acid concentration
results in muscle damage, breakdown and release of myoglobin. The dark urine color
is due to the increase in myoglobin being excreted and can cause kidney damage as it
passes through the system. Causes and Severity

A mild case of rhabdomyolosis (tying up) may result in soreness in the gluteal muscles,
a painful and stiff gait, or simply a decrease in performance. The causes may
include limited exercise, an anticipatory situation, or simply putting the horse in a
stressful environment such as trailer loading, new locations, or loading into a starting
gate or chute. In addition, young horses with viral infections (equine herpes virus
1 and influenza) have experienced bouts of tying up that were not associated with
exercise.

Horses with severe rhabdomyolosis (azoturia, acute exertional
rhabdomyolosis, black water disease) will show severe pain, reluctance to move, urination
stance, increased heart rate and sweating. These horses will pass dark red or brown
colored urine, lay down quietly or thrash in pain. Some horses may have chronic
intermittent bouts of tying up, and this may be due to electrolyte deficiencies or
imbalances. Dehydration can contribute to worsening bouts and result in greater
kidney damage as myoglobin excretion occurs. High intensity-induced bouts (a racing or
cutting competition) may be related to increased acidosis in the muscles, while glycogen
depletion, dehydration, and electrolyte imbalance may contribute to endurance
exercise-induced bouts (50 mile endurance ride). Testing

Your veterinarian can use a blood sample to test serum for levels of
myoglobin (almost immediately), creatine kinase (approximately 4-6 hours), and aspartate
aminotransferase (approximately 18-24 hours) after a suspected bout. If you suspect
that your horse may be experiencing minor bouts of tying up, it will be necessary to
establish normal values. Your vet may want to draw blood samples up to 30 minutes
prior and 4-6 hours after exercise to evaluate creatine kinase levels in the serum.
Be cautioned that diet and management can affect the values. Treatment

A mild case of tying up may be treated with a nonsteroidal anti-inflammatory (i.e.
Phenylbutazone) and rest for 3-5 days with a gradual increase in exercise. A
decrease in training intensity and grain intake will usually be recommended.
Sedatives such as Acepromazine which causes sedation and relaxation by depressing the
central nervous system, may be given to decrease the anxiety and spasms after the
horse ties up. In some chronic cases, Acepromazine may be used in a preventative
effort prior to exercise, to help promote vasodilatation or opening of the outlying blood
vessels. Veterinarians may give the horses immediate intravenous Thiamin or
intramuscular Vitamin E and Selenium injections to aid return to health or monthly
prophylactic injections to decrease potential onset of tying up episodes.

Horses exhibiting severe symptoms of rhabdomyolosis may be treated with intravenous
fluids to decrease potential kidney damage due to the myoglobin excretion and
shock. Nonsteroidal anti-inflammatory drugs and/or painkillers may be necessary
during recovery time. As with mild cases, a sedative may be used to decrease the
anxiety and help prevent thrashing or excess movement. In severe cases, it is
critical to limit movement to decrease potential permanent muscle damage. Recovery
time may be up to 6-8 weeks, and ability to return to work will vary with severity.

Horses that suffer from chronic attacks of rhabdomyolosis can often be
managed successfully with strict exercise, management and diet protocols. A diet
balanced for mineral and vitamin needs that provides a good quality hay, fresh water, and
minimal grain may be adequate to control some cases of chronic rhabdomyolosis.
Management strategies that reduce stressful situations and provide a consistent and calm
environment may help as well. Some horses may need to be maintained on sedatives
prior to exercise or daily medication to decrease or prevent muscle damage during tying up
episodes. Conclusions

Proper monitoring of conditioning, diet and management may significantly decrease or
prevent the onset of mild to severe episodes of rhabdomyolosis. While excitability
and genetics may predispose some horses to this disease, consistency in the environment,
exercise protocol, and nutrition can work toward prevention or management. Horses
that are affected with chronic rhabdomyolosis may require medication for continued use of
the horse in a productive manner. Finally, do not burden your unfit horse with
spontaneous exercise bouts (intense or endurance), as it can have a much longer and
serious effect than you had planned on.